The software should add some info about the edit when someone doesn't fill out
the edit summary field, making patrolling easier on everyone. For instance, if I
make a minor change to an article, changing "5KV" to "5 kV", I just press alt+s
out of habit, without filling out the summary. What would be ideal is if the
software just autogenerated a summary of:
16:15 Electricity (diff; hist) . . Omegatron (Talk) (→Voltage - "5KV" → "5 kV")
In cases of vandalism, this clearly labels it for those patrolling recent
changes or watchlists:
16:15 Politics (diff; hist) . . 192.1.2.123 (Talk) (→Political concerns - "is a
member of the" → "IS GAY!!!")
Since the autogenerated summary is colored, it can be trusted and can prevent
the need to waste bandwidth, time, and server load from checking a lot of diffs
by anon editors that are simple spelling fixes and such.
"But we already have a policy of encouraging edit summaries! They should be
filled in!" So what? A lot of people, especially vandals, simply don't fill
them out. It would be tremendously helpful if the software generated a crude
summary itself in these cases.
This saves precious server resources by processing a diff only once, preventing
the need for many people to load that diff again in the future.
More details and examples at the included URL.

(In reply to comment #0)
> The software should add some info about the edit when someone doesn't fill out
> the edit summary field....
This is a similar to bugzilla http://bugzilla.wikimedia.org/show_bug.cgi?id=1307
"Auto-Edit Summary: if few changes ("smaller" than a threshold) have been made,
automatically create an Edit Summary from diff results"

This is the germ of a good idea. I might not like to see the mini-diff right on
top of or sharing the edit summary field; I'd rather have another column in the
history display.
Implementation might be very tricky. The diff mechanism already tends to choke
and get confused, failing to equate large blocks of identical text. I do agree
that a mini-diff of some sort would prove extremely useful.